Hybrid computer system for rapid generation of electric power system loadflow solutions and transient stability analysis

ABSTRACT

A hybrid loadflow computer arrangement with transient stability analysis capability includes a modularized analog network simulator and a digital computer which acquires and processes online data and operator data related to a power system for which loadflow and transient stability problems are being solved. The analog simulator includes modular circuits representative of power systems buses, generators, loads, lines and tie lines interconnected to represent the power system and the interface between the digital computer and the analog network simulator is provided by analog-to-digital and digital-to-analog converters. The hybrid arrangement operates iteratively during the loadflow solution with the analog network simulator providing a bus voltage solution for a set of network simultaneous equations, as well as generator swing angle values for transient stability analysis, and the digital computer providing generator power and voltage magnitude constraints, load admittance values and power constraints, and tie bus voltage and power constraints.

United States Patent 1191 Carlson et a1.

[ 1 Aug. 13, 1974 [75] Inventors: Norman R. Carlson, Export;

William E. Zitelli, Pittsburgh, both 235/l5l.l, 184; 307/18, 19, 20, 24, 30, 31, 38, 52, 62; 444/1; 340/1725 [56] References Cited UNITED STATES PATENTS 3,341,697 9/1967 Kaufman et al. 235/1505 X 3,582,628 6/1971 Brussolo 235/1505 3,675,002 7/1972 Mitsui et al 235/184 X 3,699,538 10/1972 Van Essen 340/1725 X 3,701,891 l0/l972 Cohn 235/184 X OTHER PUBLICATIONS Load Flows by Hybrid Computation for Power System Operations; M. Enns, T. C. Giras, & N. R. Carlson, IEEE Transactions on Power Apparatus and Systems, Nov/Dec. 1971, pp. 2540-2547.

Techniques for the Real-Time Monitoring of Power System Operations; G. W. Stagg, J. F. Dopazo, O. A. Klitin, & L. S. Vanslyck; IEEE Transactions on Power Apparatus and Systems, Vol. PAS-89, No. 4, April Load Flows Using a Combination of Point Jacobi and Newtons Methods, Y. P. Dusonchet, S. N. Talukdar, H. E. Sinnot; IEEE Transactions on Power Apparatus and Systems; Vol. PAS-90, No. 3, May/June 1971, pp. 941-949.

Computer Control of Power Systems; The Engineer, Oct. 2, 1964.

Primary ExaminerMalcolm A. Morrison Assistant Examiner-Edward J. Wise Attorney, Agent, or FirmE. F. Possessky [5 7] ABSTRACT A hybrid loadflow computer arrangement with transient stability analysis capability includes a modularized analog network simulator and a digital computer which acquires and processes on-line data and operator data related to a power system for which loadfiow and transient stability problems are being solved. The analog simulator includes modular circuits representative of power systems buses, generators, loads, lines and tie lines interconnected to represent the power system and the interface between the digital computer and the analog network simulator is provided by analog-to-digital and digital-to-analog converters. The hybrid arrangement operates iteratively during the loadflow solution with the analog network simulator providing a bus voltage solution for a set of network simultaneous equations, as well as generator swing angle values for transient stability analysis, and the digital computer providing generator power and voltage magnitude constraints, load admittance values and power constraints, and tie bus voltage and power constraints. 1

9 Claims, 41 Drawing Figures INJECTION CURRENT VALVES TRAN M1 N L|NE OUTA-GE SWITCHING, i gfifi SIMULATOR AID q- W LOAD,TIES, GENERATION BUS VOLTAGE VALVES v LINES BUSES TRANSFORMERS PAIENIEDAWW 3.829.667

SREH '01 0f 23 NORTH l9 4 l3 I 325 I EHV(50OKV 3a) 4 5 3 L LOAD I l 34 I PHILADELPHIA f I4 BUFFALO 2s LOAD EHV WASHINGTON r 22 /96 v 23 WHEELING [9 WEST I LOAD F|G.l

INJECTION CURRENT VALVES J f 4 D/A /40 TRANSMISSION I INE OUTAGE SWITCHING NETWORK SIMULATOR A/ E I D F 4/ T O BUS VOLTAGE VALVES LINE$.BUSES GENERATION TRANSFORMERS PAIE'NTEUAUBI awn 3. 829.667

SWEU "02 Bf 23 BUS l 30 I BIG 1,; z e INTEGRATOR 5P w l 1 I l 320 (314 I ADMITTANCE i -(E -Eq) {Q 306 LINE -q) 323 322' 3l 6 AOMI TANOE I pr LN I (E -E 1 F306 LINEI -n) i I l I l [325 3 FIGS )4 ADMITTANCE O Y p p 306 LlNE(p-n) LINE OUTAGE SWITCHING F ANALOG I A06 4Ia- DIGITAL D/A GENERATION *gfig COMPUTER POWER [5% AND LINE VOLTAGE MODULES [E] MODULES SET POINTS 1 J BUS VOLTAGES AND LINE cuRRENT 'sOLuTION P164 P so P r r 1 YQ L PL S E r V p Pp v TOBUS-P ps Er 73 2 7| L lp a li z 5 I 1 7O 5 i 74 (E1 FIG.5 E P E\ PATENTED M19 1 31974 3 829 667 sum fun or 23 I v |2| W 123 PsL PsL

LINE I TO BUS5 LINE I FROM 22 BUS BUSES (TRANSFORMER) 6 j LINE T FROMI/O TOBUS9 TO BUS 7 LOAD 26 FROM 1/0 I v GENERATOR FlG.9

ANALOG FAULTING MODULES CIRCUITRY PANEMMANUAL) DIGITAL CONTROL FIG IOA PATENTEII AUG I 3 I974 SHEET Os 0F 23 LINE OUTAGE SWITCHING A/D BUS VOLTAGE AND LINE CURRENT SOLUTIONS 4'0 4l3 4l2 7 4 I D/A ANALOG [E] ANALOG [E] DIGITAL POWER DYNAMIC BUS ANALOG COMPUTER VOLTAGE GENERATOR LINE A LOADS SET POINTS MODULES [1G] MODULES [IT] SWING ANGLES [E] ROTATIONAL vELolTlEs 4l4 D/A INFINITE BUS VOLTAGE kfig sET POINTS INFINITE BUSES DCU'S FORLOAD ADMITTANCE ADJUSTMENTS FIG, IO

LINE CURRENT AND 4V3 BUS VOLTAGE soLuTIoNs 1 [4'0 [4" WA [16] U DIGITAL ANALO COMPUTER LINE OUTAGE fiE LOADS? SWITCHING [1L] IE] [IT] ANALOG TIES AND INFINITE BUSES FIG II DcU's LOAD ADMITTANCE ADJUSTMENT FAULTING DEVICE 33o FBI K 326 FAULTING 344 30s DEVICE 304 336 333 1 .1 KA KBI K EM FIG.I2

PAIENIEB AUG 3 I974 SHEET 08 0F 23 I H H o o H 'H H In; 44......

PATENTEBNJBI 3mm 3,829,667

SHEET '1' 0? 0F 23 345 FAULTING DEVICE FAULTING DEVICE ULTING VICE , FAULTING DEVICE mamzuwm 3,829,667

REAL BUS VOLT INPUT IMAG I NARY BUS VOLT PAIENIEmusxazsm 39829667 I saw war 2s R307 I I R3l0 5 a v Pmmmmmzsu I 3 p 9 5 saw 710 or 23;

ALB

PAIENTEIJ I 3,829.66? sum 12oF 23 v INTRONICS MULTIPLIER INTRONICS MUL'I'IPLIERv PAIENTEnAum 3:914

sum '13 or 23 GENERATOR o o BUS LOAD --(7Q BUS 728 FIG. 20

PATENTED N 3 74 SlOl-SIOS SHEET T9 T I II I T M I IT TI I v TYPICAL TYPICAL |2O2/ GENERATOR LOAD MODULE M DULE FIG. 22A. FIG. 228.

DIGITAL COMPUTER cco 4223 I208 |209 I2IO I22I Q22 I226 I230 I23I [D/A ccq cco FO D] 0(5)] PVAR WATTfi 551 [OcOj D/A I v I f V BUS GENERATOR LOAD LINE TIE LINE MODULE MODULE MODULE MODULE MODULE Izoe I2I5 I220 2 5 Y |A/Dl/l2l8 f/E ma IZIQ iA/D! FIG. 27

PAIENTED 3W4 SHEET D/A INF. BUS VOLTAGES D/A IEI, M GENERATOR SET POINTS MODELS 7 [G DATA UNE TRANSFO RNEL [IT].

SWITCHING 983 LlNK A/DANALOG NET SIMULATOR I SOLUTION [E] 982 L] LOAD ADMITT. LOAD SETTINGS MODELS SYSTEM STUDY OPERATORS MODE 

1. A hybrid loadflow computer arrangement with transient stability analysis capabiLity comprising a D.C. analog simulator of an A.C. power system said simulator including a plurality of D.C. circuits interconnected to correspond to the A.C. network, a digital computer, said digital computer including means for determining representations of data corresponding to predetermined network variables, said digital computer including means for generating signals representative of said data to said simulator, said computer and said simulator including means for generating a loadflow solution with use of said data representations, said computer including means for applying representations of one or more transient faults on said analog simulator D.C. circuits after a loadflow solution has been reached, and said digital computer including means for detecting outputs from said simulator to determine transient network responses and network stability resulting from the imposed faults.
 2. A hybrid loadflow computer arrangement as set forth in claim 1 wherein said plurality of D.C. circuits includes bus, generator, load, tie line and line D.C. circuits interconnected to correspond to the A.D. network.
 3. A hybrid computer arrangement as set forth in claim 2 wherein each of said bus D.C. circuits includes means for responding to generator, load, tie line and line phasor current input signals and for generating an output bus voltage phasor signal.
 4. A hybrid computer arrangement as set forth in claim 2 wherein each of said generator D.C. circuits includes means for responding to the difference between generator mechanical power and generator electrical power input signals and the difference between generator terminal voltage input signals and bus voltage phasor input signals, and for generating a generator swing angle output signal, a generator rotational velocity output signal and a generator phasor current output signal.
 5. A hybrid computer arrangement as set forth in claim 2 wherein each of said load D.C. circuits includes means for responding to applied bus voltage phasor signals, means for receiving and representing first and second load admittance signals, and means for generating a bus to load current phasor output signal.
 6. A hybrid computer arrangement as set forth in claim 2 wherein each of said tie line and line D.C. circuits includes means for responding to the difference between applied bus voltage phasor signals and generating an output line phasor current signal in accordance with at least the equivalent series branch impedance.
 7. A hybrid loadflow computer arrangement with transient stability analysis capability comprising a D.C. analog simulator of an A.C. network, said simulator including a plurality of bus D.C. circuits, generator D.C. circuits, load D.C. circuits, tie line D.C. circuits and line D.C. circuits interconnected to correspond to the A.C. network, a digital computer, said digital computer including means for determining representations of generator mechanical powers and generator terminal voltage magnitudes, first and second load admittances for each load, load real and reactive powers, external tie bus voltages and tie line real and reactive powers, said computer including means for generating representative signals of said generator mechanical powers and generator terminal voltage magnitudes, said first and second load admittances for each load and said external tie bus voltages, means for applying said representative signals to corresponding generator, load and tie line D.C. circuits to said simulator, each of said bus D.C. circuits including means for responding to generator, load, tie line and line phasor input current signals and for generating an output bus voltage phasor signal, each of said generator D.C. circuits including means for responding to the difference between generator mechanical power and generator electrical power input signals and the difference between generator terminal voltage input signals and bus voltage phasor input signals, and for generating a geNerator swing angle output signal, a generator rotational velocity output signal and a generator phasor current output signal, each of said load D.C. circuits including means for responding to applied bus voltage phasor signals, means for receiving and representing first and second load admittance signals and means for generating a bus to load current phasor output signal, each of said tie line and line D.C. circuits including means for responding to the difference between applied bus voltage phasor signals and generating an output line phasor current signal in accordance with at least the equivalent series branch impedance, one of said applied bus voltage phasor signals to each of said tie line circuits being a digital computer determined external tie bus voltage signal, said digital computer and said analog simulator including means for generating a loadflow solution through determining in successive iterations first and second load admittances as a function of load power and bus to load voltage values in the next preceding iteration and determining in successive iterations external tie bus voltages as a function of tie line power and current values in the next preceding iteration, said computer including means for applying representations of transient faults on said bus, generator, load, tie line and line D.C. circuits after a loadflow solution has been attained, and said computer including means for detecting outputs from said simulator to determine transient network responses and network stability resulting from the imposed faults.
 8. A method for making a transient stability analysis in a hybrid loadflow computer arrangement with transient stability analysis capability comprising the steps of operating a digital computer to determine representations of data corresponding to predetermined A.C. network variables, operating said digital computer to generate signals representative of said data to a D.C. analog simulator including a plurality of D.C. circuits interconnected to correspond to said A.C. network, operating said computer and said simulator to generate representations of a loadflow solution with use of said data representations, operating said computer to apply representations of one or more transient faults on said analog simulator D.C. circuits after a loadflow solution has been reached, and operating said computer to monitor outputs from said simulator to determine transient network responses and network stability resulting from the imposed faults.
 9. A loadflow computer arrangement with transient stability analysis capability comprising a D.C. analog simulator including a plurality of D.C. circuits interconnected to correspond to the A.C. network, said plurality of D.C. circuits having means for receiving signals representative of predetermined network variables for generation of a loadflow solution with use of said signals, and means for receiving and responding to imposed transient fault signals after a loadflow solution has been reached to generate transient network response signals for transient stability monitoring. 